Searchlight of the high-pressure arc lamp-type having automatic shutter means

ABSTRACT

A searchlight comprising a high-pressure compact arc-type arc lamp containing a high-pressure ionizable atmosphere and a pair of electrodes spaceable from each other for establishing an arc discharge therebetween a reflector mounted on the lamp with the portion of the lamp containing the arc producing ends of the electrodes positioned in the reflector at the reflector optical axis e.g., at the focal point, an automatic shutter for instantaneously shielding the after glow of the lamp when the lamp operating current is interrupted or shutoff, the shutter being in the form of a shielding tube reciprocatingly movable over the lamp along the lamp axis to selectively cover and uncover the arc discharge providing ends of the electrodes.

United States Patent [72] inventor DietmarM.Schoeffel Hillsdale, N .J [21] AppLNo, 837,121

[22] Filed June 27, 1969 [45] Patented Nov. 30, 1971 [73] Assignees Schoeffel Instrument Corporation Westwood, NJ.

Canrad Precision Industries Pelham, N.Y. part interest to each [54] SEARCHLIGHT OF THE HIGH-PRESSURE ARC LAMP-TYPE HAVING AUTOMATIC SHUTTER 46 03, 46.11. 46.21, 46.23, 46.25, 46.29, 4] ARC; 335/227. 251, 279, 261

1 References Cited Primary Examiner-Richard C. Queisser Assistant Examiner Ellis J. Koch Attorneys-Samuel Kahn and John G. Kovalich ABSTRACT: A Searchlight comprising a high-pressure compact arc-type arc lamp containing a high-pressure ionizable atmosphere and a pair of electrodes spaceable from each other for establishing an arc discharge therebetween a reflector mounted on the lamp with the portion of the lamp containing the are producing ends of the electrodes positioned in the reflector at the reflector optical axis e.g., at the focal point, an automatic shutter for instantaneously shielding the after glow of the lamp when the lamp operating current is interrupted or shutoff, the shutter being in the form of a shielding tube reciprocatingly movable over the lamp along the lamp axis to selectively cover and uncover the arc discharge providing ends ofthe electrodes.

PATENIEDuuvsomn 3524.600

INVIZN'I'UR.

D/ETMAR M SCHOEFFEL a ux AGENT SEARCHLIGIIT OF THE HIGH-PRESSURE ARC LAMP- TYPE HAVING AUTOMATIC SI-IU'I'IER MEANS BACKGROUND OF THE INVENTION Compact arc lamps of the type containing electrodes spaced apart less than about 1 cm. in an ionizable atmosphere comprising rare gas, e.g., xenon, at a pressure above about 2 atmospheres, e.g., 3-12 temperatures of about 25 C. have been used as light sources of high intensity, e.g., in searchlights. Such searchlights find application, for example, in signalling. When the lamps are extinguished, there still remains an after glow from the still hot electrodes for a considerable period of time.

This application proposes to provide a means for instantaneously eliminating the lamp after glow when the lamp operating current is shutoff.

SUMMARY OF THE INVENTION The invention deals with a searchlight comprising a high pressure are lamp containing a high-pressure ionizable atmosphere and a pair of electrodes spaceable from each other, for example, in a fixed spaced relationship defining an arc gap or otherwise adjustably spaceable from each other for establishing an arc discharge therebetween, a reflector is mounted on the lamp with a portion of the lamp containing the are producing ends of the electrodes positioned in the reflector at the reflector optical axis, e.g., at the reflector focal point, an automatic shutter for instantaneously shielding the lamp electrode after glow of the lamp when the lamp operating current is interrupted or shutoff, the shutter being in the form of a shielding tube composed of magnetic composition, e.g., the metal of a solenoid armature, reciprocatively movable over the lamp envelope along the lamp axis to selectively cover and uncover the arc discharge providing ends of the electrodes, a solenoid coil is mounted over the shielding tube coaxially of the tube with the tube being the solenoid annature, the tube annature being of gradually increasing mass along its axis in the direction of the lamp arc producing ends of the electrodes. The gradually increasing mass is provided, e.g., by at least one elongated aperture along the tube axis with the aperture being shaped to diminish from one end to the other in the direction of the arc producing electrode ends, and the aperture being located within the magnetic field of the solenoid coil. Otherwise, the tube may be provided along its axis with a plurality of holes of gradually increasing size in lieu of the above-described aperture shape.

DESCRIPTION OF THE DRAWINGS The single FIGURE of the drawings illustrates a partly elevational, partly schematic and partly cross-sectional view of a searchlight assembly according to the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the FIGURE, the invention comprises a tubular fused quartz envelope 1 having opposite end portions 2 and 3. An anode assembly is hermetically sealed into end portion 2. The anode assembly comprises a molybdenum seal foil 4 having an input lead 5 welded to one end thereof and a tungsten anode electrode 6 mounted inside the envelope on one end of a stem 7 with the other end of the stern being welded to the opposite end of seal foil 4.

A cathode assembly is hermetically sealed into end portion 3. The cathode assembly comprisesa molybdenum seal foil 8 having an input lead 9 welded to one end thereof and an elongated cathode electrode 10 mounted inside the envelope with one end welded to the other end of seal foil 8 and extending axially of the envelope toward the anode 6 sufficiently to provide an operable arc gap 11. The envelope contains a highpressure ionizable atmosphere, e.g., xenon at a pressure above about 2 atmospheres at a temperature of about 25 C. as hereinbefore stated. A parabolic type reflector I2 is mounted on the lamp envelope I with a portion of the lamp containing the arc producing ends of cathode 10 and anode 6 positioned in the reflector at the reflector optical axis, e.g., at the reflector focal point. An automatic shutter for instantaneously shielding the lamp electrode after glow as hereinbefore described is mounted on the lamp envelope. The shutter is in the form of a shielding tube 13 composed of magnetic metal composition and slidably mounted over the lamp envelope and extends into the reflector 12 so that reciprocating movement over the lamp along the lamp axis selectively covers and uncovers the arc producing ends of the electrodes 6 and 10. A solenoid coil 14 is coaxially mounted over the tube 13 with the tube performing as a solenoid armature, and the tube 13 being slidably movable between the coil 14 and the lamp envelope 1. The tube armature is essentially characterized by at least a portion 15 thereof of gradually increasing mass along the tube axis with the mass of the portion 15 increasing in the direction of the arc producing ends of the electrodes. The solenoid coil 15 positioned over the tube armature at a location where the gradually increasing mass portion of the tube is under the influence of the magnetic field of coil 14 thereby permitting the tube to function as an armature. The gradually increasing mass of the tube 13 is provided, e.g., by at least one elongated aperture 16 along the tube axis with the aperture being shaped to diminish from its one end to its other end in the direction of the arc producing electrode ends and the aperture being located within the magnetic field of the solenoid coil 14. Otherwise, the tube may be provided with a plurality or series of axially spaced holes therethrough of gradually decreasing size in lieu of the shaped aperture 16. The tube 13 is further provided with a spring abutment means, e.g., in the form of a fin 17 extending radially outward of the tube outer surface preferably at a location between the reflector and the solenoid coil 14. A spring support means, e.g., in the form of a tubular shell 18, is coaxially mounted over the lamp 1 and radially spaced therefrom. Preferably the spring support means is mounted over coil 14 and contains a spring seat 19 with a helical spring 20 being positioned on the spring seat 19 and abutting the tube abutment means 17. The lamp is operated by a source of DC current 21. A conductor 22 is connected to the source of current and is connectable to the cathode lead 9. A switch 23 is provided in conductor 22. Another conductor 24 is connected to the source of current and is connectable to the anode lead 5. An electrical conductor 25 is connected betweert conductor 22 and one end of solenoid coil 14. Another conductor 26 is connected between conductor 24 and the other end of solenoid coil 14. One of the coil conductors e.g., conductor 26 is provided with a current limiting means illustrated as a resistance 27 should the coil 14 require less current than that provided to the lamp by the source of current 21.

In operation, when switch 23 is closed, the lamp electrodes 6 and 10 are energized and produce an are between the electrodes to ignite the lamp. At the same time e.g., instantaneously, solenoid 14 is energized and its magnetic field causes armature tube 13 to move away from and to instantaneously uncover the arc gap 7 with the tube moving from position A to position B and compressing spring 20. The tube 13 assumes position B while the lamp is in operation. When it becomes desirable to extinguish the lamp, the switch 23 is opened, as illustrated, and the compressed spring 20 abutting the tin 17 instantaneously causes the tube 13 to again cover the electrode gap 11 thereby instantaneously shielding the still glowing electrode ends from sight, thus eliminating the lamp electrode after glow hereinbefore described.

lclaim:

1. The combination of a high-pressure-type arc lamp and an automatic shutter for electrode afterglow comprising, an arc lamp of the high-pressure type having a light-transmissive envelope containing an ionizable atmosphere and electrodes having end portions for defining an arc therebetween; an electrode afterglow shutter in the form of a tube of magnetic material slidably coaxially mounted over at least a portion of the lamp envelope for displacement between a first position at which an end portion of said tube shields said end portions of said electrodes and a second position spaced from said first position at which said tube end portion is out of registration with said end portions of said electrodes; a solenoid coil coaxially mounted over said tube, said tube defining a solenoid armature and being formed with at least a portion thereof of gradually increasing mass as viewed along said tube axis in the direction of said electrode and portions; and means for normally biasing said end portion of said tube in said first position, said solenoid coil being positioned over said armature tube at a location at which the portion of said tube of gradually increasing mass is subjected to the influence of the magnetic field of said solenoid coil for the displacement of said solenoid coil from said first to said second position upon the energization of said coil.

2. A searchlight of the high-pressure arc lamp type having automatic shutter means for electrode afterglow comprising an arc lamp of the high-pressure type having a light-transmissive envelope containing an ionizable atmosphere and electrodes having end portions for defining an arc therebetween; a reflector mounted on the lamp with at least a portion of the lamp containing the are defining the ends of the electrodes positioned in the reflector along the reflector optical axis; an electrode after-glow shutter in the form of a tube of magnetic material slidably coaxially mounted over at least a portion of the lamp envelope and extending into the reflector for displacement between a first position at which an end portion of said tube is located in said reflector to shield said end portions of said electrodes and a second position at which said end portion of said tube is positioned out of registration with said end portions of said electrodes; a solenoid coil coaxially mounted over said tube rearwardly of said reflector, said tube being a solenoid an'nature formed with at least a portion thereof of gradually increasing mass as viewed along the tube axis in the direction of said electrode and portions; and means for normally biasing said tube in said first position, said solenoid coil being positioned over said armature tube at a location at which said portion of said tube of gradually increasing mass is subjected to the magnetic field of the coil for the displacement of said tube from said first to said second position upon the energization of said coil.

I i l II 

1. The combination of a high-pressure-type arc lamp and an automatic shutter for electrode afterglow comprising, an arc lamp of the high-pressure type having a light-transmissive envelope containing an ionizable atmosphere and electrodes having end portions for defining an arc therebetween; an electrode afterglow shutter in the form of a tube of magnetic material slidably coaxially mounted over at least a portion of the lamp envelope for displacement between a first position at which an end portion of said tube shields said end portions of said electrodes and a second position spaced from said first position at which said tube end portion is out of registration with said end portions of said electrodes; a solenoid coil coaxially mounted over said tube, said tube defining a solenoid armature and being formed with at least a portion thereof of gradually increasing mass as viewed along said tube axis in the direction of said electrode and portions; and means for normally biasing said end portion of said tube in said first position, said solenoid coil being positioned over said armature tube at a location at which the portion of said tube of gradually increasing mass is subjected to the influence of the magnetic field of said solenoid coil for the displacement of said solenoid coil from said first to said second position upon the energization of said coil.
 2. A searchlight of the high-pressure arc lamp type having automatic shutter means for electrode afterglow, comprising an arc lamp of the high-pressure type having a light-transmissive envelope containing an ionizable atmosphere and electrodes having end portions for defining an arc therebetween; a reflector mounted on the lamp with at least a portion of the lamp containing the arc defining the ends of the electrodes positioned in the reflector along the reflector optical axis; an electrode after-glow shutter in the form of a tube of magnetic material slidably coaxially mounted over at least a portion of the lamp envelope and extending into the reflector for displacement between a first position at which an end portion of said tube is located in said reflector to shield said end portions of said electrodes and a second position at which said end portion of said tube is positioned out of registration with said end portions of said electrodes; a solenoid coil coaxially mounted over said tube rearwardly of said reflector, said tube being a solenoid armature formed with at least a portion thereof of gradually increasing mass as viewed along the tube axis in the direction of said electrode and portions; and means for normally biasing said tube in said first position, said solenoid coil being positioned over said armature tube at a location at which said portion of said tube of gradually increasing mass is subjected to the magnetic field of the coil for the displacement of said tube froM said first to said second position upon the energization of said coil.
 3. A searchlight according to claim 2, wherein the tube carries an abutment means, a support means for the biasing means coaxially mounted over the lamp envelope, the support means and the abutment means being spaced from each other axially of the tube and positioned rearwardly of the reflector, the biasing means being positioned between the support and the abutment means.
 4. A searchlight according to claim 3, wherein the abutment means is in the form of a fin extending radically outward of the tube outer surface.
 5. A searchlight according to claim 2, wherein the portion of gradually increasing mass is provided by at least one elongated aperture shaped to diminish from its one end to its other end in the direction of the said electrode end portions, and the aperture being located within the magnetic field of the solenoid coil. 